This invention relates to a tandem seal for precluding fluid leakage from the circumferential space between a shaft and a housing. It includes an end face seal uniquely coupled to a dynamic pressure generating seal. During static conditions, the end face seal precludes loss of fluid. During rotation of the shaft the dynamic seal precludes loss of fluid and disengages the end face seal.
Mechanical end face seals have become an accepted device to seal the circumferential space between a shaft and a housing. Such seals include two seal washers. One is mounted in sealing engagement on the shaft and is usually biased axially towards the housing. The other washer is fixed to the housing. The two washers have radially extending faces in rotating contact which are sufficiently flat to preclude fluid leakage. While such seals are quite acceptable, they do utilize energy. The rotating contact between the faces results in undersirable friction losses.
The loss has been previously recognized and attempts have been made to eliminate it. One prior design is illustrated by U.S. Pat. No. 1,947,017. In that design, the patentee uses an end face seal to preclude loss of fluid during the static - non-operating condition of the pump. Upon rotation of the shaft, a hydraulic cylinder responding to fluid pressure disengages the end face seal and a separate repeller is used to limit or preclude leakage from between the pump housing and the shaft. This design is complicated. It requires a separate repeller and chamber in the pump housing. It also requires an external pressure sensing chamber, a separate hydraulic cylinder and complicated linkages. Another design is sold by the Sealol Company. As depicted in the brochure attached to this application, this design also utilizes a separate repeller and sophisticated pressure sensing chamber.
Our invention is a tandem seal preferably arranged in cartridge form which can be installed in existing pump housings. It eliminates the use of a separate repeller, modification of the pump housing casting to include a repeller chamber and incurs minimum power losses in effecting its sealing function. Wear and seal part replacement problems are substantially eliminated.